The proposed research will contribute to a better understanding of the role postnatal experience has in the development of the brain. This will be approached through the study of the olfactory system which, by virtue of its unique structural organization and ontogeny, is ideally suited for experimental analyses of the problem. Specifically, the proposed experiments will use anatomical and metabolic mapping methods to examine the consequences of unilateral neonatal olfactory deprivation upon the subsequent proliferation and death, organization, and functional activity of nerve cells in the olfactory system. The goals are to learn which neural elements are most responsive to environmental influences, to reveal the nature and range of those responses, and to determine the extent to which those responses can be further modified (i.e. reversed) in adults. Our hope is that these experiments will not only elucidate the role of early experience in the development of the olfactory system, but also provide insights into the basic mechanisms that govern the response of developing nervous systems to early experience.